1. Field of the Invention
The present invention relates to a power source used for a computer or the like. More particularly, the invention relates to a heat sink and a power source unit employing the same which can minimize leakage of plosive outside of the power source unit upon failure of semiconductor parts.
2. Description of the Related Art
In the power source unit to be used in computers or the like, a switching MOSFET which is a semiconductor part frequently causing failure, is employed. Since the switching MOSFET operates at high voltage and high power, a large amount of plosive and momentary sparks can be caused upon occurrence of failure of the MOSFET. In order to adapt to such failure, the power source unit is designed not to cause fire on the basis of safety standard.
FIG. 3 is a perspective view of the conventional type heat sink. The heat sink 1 shown in FIG. 3 is formed with a flat plate 1a of aluminum with a plurality of fins 1b. The heat sink 1 thus constructed is mounted so that it extends substantially perpendicular to planes of a printed circuit board. A semiconductor part 3, such as a switching MOSFET, is secured on an aluminum plate 2 at back surface portion for performing cooling by radiating heat of the semiconductor part 3 by the heat sink 1.
In case of the power source unit using the heat sink 1, the semiconductor part per se is mounted on the printed circuit board in bare condition within the power source unit. Since the power source unit is cooled by air, ventilation opening is formed in a casing. On the other hand, in case of the computer or the like, since the power source unit is mounted at a position facing outside of a main body, the semiconductor part (switching MOSFET) of the power source unit cannot be said as being shielded.
Therefore, since the switching MOSFET caused failure at high frequency, burst is caused in the switching MOSFET, plosive should directly cause leakage to outside of the main body. Then, user may hear a large amount of plosive, may see momentary sparks flying out or smoke flowing out of the computer or the like, or may smell odor to cause serious discomfort for the user. Nowadays, concern for product liability is growing, even though occurrence of sparks does not lead to occurrence of fire actually, such failure may cause degradation of credibility to result in re-calling of whole products.
The present invention has been worked out in view of the problems set forth above. It is therefore an object of the present invention to provide a heat sink can minimize leakage of plosive outside of the power source unit upon failure of semiconductor parts and can restrict leakage of flash, odor, smoke and so forth which is possibly caused upon occurrence of failure of the semiconductor parts, and a power source unit employing such heat sink.
According to the first aspect of the present invention, a heat sink comprises:
a heat radiating casing housing therein a semiconductor part forming a power source unit therein, and whereby sealing the semiconductor part within the casing.
In the preferred construction, fins may be provided on an outer surface of the casing. The semiconductor part may be mounted on the inner surface of the casing. The casing may be mounted on a printed circuit board and the semiconductor part is connected to the printed circuit board. At least one of side walls of the casing may be formed with a nonflammable transparent plate. The semiconductor part may generate plosive upon failure of semiconductor part. In this case, a sound deadening sheet of nonflammable material may be fitted on an inner surface of the casing.
According to the second aspect of the present invention, a power source unit comprises a heat sink constructed as set forth above. Namely, the power source unit includes a box shaped heat sink housing therein a semiconductor part forming a power source unit therein, and whereby sealing the semiconductor part within the heat sink.
As set forth above, with the heat sink and the power source unit employing the same seals the semiconductor part, such as switching MOSFET with the box shaped heat sink to insulate from the outside of the heat sink. Therefore, even when failure is caused in the semiconductor part, plosive thus generated can be suppressed within the heat sink so as not to reach a user""s ears, and flash, foreign odor, smoke and so forth will never leak out. Thus, failure of semiconductor part will never provoke anxiety of the user.